Circuit maintenance and the correct use of electric soldering irons
1. Gripping method of electric soldering iron
① Brushstroke technique
The pen grip method is suitable for low-power and straight soldering iron heads, and is suitable for welding soldered parts with low heat dissipation, such as printed circuit boards in welding instruments. The grip technique is the most commonly used method for instrument workers.
② Positive grip method
The positive grip method is suitable for electric soldering irons with relatively large and curved soldering iron tips. Can be used for soldering when the circuit board is perpendicular to the desktop.
③ Reverse grip method
The reverse grip method is to hold the handle of an electric soldering iron in the palm with five fingers. This method is suitable for high-power electricity, soldering iron, and welded parts with large heat dissipation.
2. Select electric soldering iron according to its purpose
When soldering conventional components on printed circuit boards, such as diodes, transistors, resistive and capacitive components, and integrated circuits, it is advisable to use a 20-30W internally heated soldering iron. Newcomers are advised to use 20W due to slow welding speed. When welding devices with thick pins or large area grounding points on printed circuit boards or power type connectors, it is advisable to use a 45-75W soldering iron to ensure the firmness between the soldered components and the printed circuit board or wires. It is not possible to use a low-power soldering iron to weld the solder joints of large electronic components. Due to the fast heat dissipation, the temperature of the soldering iron head drops quickly, which will form solder deposits. It appears to be soldered, but in reality, it is a virtual soldering. Welding general electronic components onto printed circuit boards with a high-power soldering iron often burns copper foil lines or electronic components.
3. Mastering the correct welding steps
The level of welding determines the stability and reliability of the repaired instrument. Quality issues with small solder joints may cause the entire instrument or control system to malfunction, and the fault points are generally extremely concealed. So mastering the correct welding steps is the key to ensuring welding quality. Now let's introduce it.
① Place the soldering iron tip at the pins of the component to be soldered and heat the solder joint first. After the solder joint reaches the appropriate temperature, promptly melt the rosin solder wire on the solder joint.
② After the tin is melted, the soldering iron head should be slightly moved according to the shape of the solder joint, so that the solder evenly fills the solder joint and penetrates into the gaps of the soldered surface. After melting an appropriate amount of solder, the solder wire should be quickly removed.
③ When the solder on the solder joint is almost full, the flux has not completely evaporated, the temperature is appropriate, and the solder is brightest and has the strongest fluidity, quickly move the soldering iron head along the direction of the component pins. When it is about to leave, quickly bring it back and leave the solder joint to ensure that the surface of the solder joint is bright, smooth, and free of burrs. Finally, use diagonal pliers to cut off the excessively long component pins, and expose the solder joints slightly.
The time for the operation process in steps ① - ② above should be controlled within 2-3 seconds. Beginners usually have a longer welding time, and a longer heating time may damage the copper foil on the printed circuit board and cannot be repaired. The third step plays a decisive role in the quality of the solder joint, and it is important to practice and understand its essentials.
